This book discusses several methodological problems in traffic psychology which are not currently recognized as such. Summarizing and analyzing the available research it is found that there are a number of commonly made assumptions about the validity of methods that have little backing and that many basic problems have not been researched at all. Suggestions are made as to further studies that should be made to address some of these problems. The book is primarily intended for traffic/transport researchers but should also be useful for specialized education at a higher level (doctoral students and transportation specialists) as well as officials who require a good grasp of methodology to be able to evaluate research.